Agatha Jansenius, later the wife of Fitzwilliam Bennet Darcy, was the daughter of a Hungarian Jew named Karoly who immigrated to the United Kingdom in company with her brother John, who made his fortune in England after converting to Christianity. In Tarzan Alive, Philip José Farmer identifies her as the original of the Mrs. Wylie who appears in George Bernard Shaw's novel An Unsocial Socialist. Mr. and Mrs. Darcy were the parents of Athena ("Agatha" in Shaw's novel), Duchess of Greystoke.
Win Scott Eckert, in his introduction to "Jongor in the Wold Newton Universe", a deleted passage from Doc Savage: His Apocalyptic Life published in Farmerphile no. 12, identifies Delhi Darcy as a daughter of Fitzwilliam Bennet Darcy and his wife (rather than Darcy's sister, as Farmer had originally theorised.
Tarzan Alive also states that Rudolf Rassendyll was the cousin of the Duchess's son John, which suggests that Rudolf's mother was also a daughter of the Darcys.